mtbc | Cheap indoor distance swimming

I think that my swimming has slowed such that some mornings I swim less than a mile; never mind. I was thinking about how to continue swimming in the longer term and I wondered to what extent one may swim in even a small pool simply through being harnessed to a bungee cord and staying in place, rather more cheaply than having the water moving fast instead. Some googling does reveal tethers and suchlike though to what extent a reasonable stroke can still be approximated I'm not sure. There also seem to be towable underwater parachutes which obviously still entail some movement, just slower.